Copper-zirconium-hafnium alloys



Patented Jan. 30, 1962 fiicc 3,019,102 COPPER-ZIRCONIUM-HAFNIUM ALLGYSMatti J. Saarivirta, Plainfield, N.J., assignor to American MetalClimax, Inc, New York, N.Y., a corporation of New York No Drawing. FiledAug. 19, 1960, Ser. No. 50,577 4 Claims. (Cl. 75-153) This inventionrelates to copper base alloys and more particularly to ternary alloyscontaining copper, zirconium and hafnium. The object of the invention isto provide an improved copper base alloy having superior strength andductility properties at elevated temperatures.

Briefly stated, the alloys of the present invention are age hardenableand contain from 0.02 to 0.15% by weight of zirconium 0.1 to 1.2%hafnium, the balance being copper which is preferably initially oxygenfree though any deoxidized copper may be u ed in making the alloy. Withappropriate processing as will be hereafter described, the alloys aresuitable as electrical and thermal conductor material useful in avariety of applications as, for example, the making of commutatorsegments, contactor plates and wires, welding tips and wheels, and thelike.

In making the alloys of the present invention, it is essential thatoxygen-free copper be used. Although any chemically deoxidized coppersuch as phosphorus or lithium deoxidized copper is generallysatisfactory for use in making the alloy, it is preferred to use copperwhich is substantially oxygen free without requiring treatment with anyof the conventional chemical deoxidants. Cathode copper is accordinglyparticularly suitable as is copper which has been produced in a reducingatmosphere such as OFHC brand copper, copper prepared in an inertatmosphere, under charcoal cover, or in a vacuum.

The alloys are made following conventional alloying practices utilizinga protective gas cover during melting of the copper, alloying andcasting operations. By way of illustration, the copper is first meltedunder argon or other suitable protective gas cover in an alloyingfurnace such as an Ajax induction furnace using a graphite crucible.With the copper melt at a temperature of from 1250 to 1300 C., thealloying ingredients are added either successively or simultaneouslyusing appropriate amounts of zirconium and hafnium in any suitable formfor alloying purposes. Zirconium and hafnium as metal, sponge and masteralloys of the respective metals with copper are illustrative of some ofthe materials that may be used in making the ternary alloys of thepresent invention. After alloying, the melt is held at temperature for afew minutes following which the alloy is cast into graphite or any othersuitable molds. No difiiculty is experienced in producing soundcastings.

Although alloys containing from 0.02 to 0.15% zirconium and from 0.1 to1.2% hafnium, balance copper with its incidental impurities provide newand useful alloys possessing generally improved properties, it has beenfound that best results are obtained when the alloy contains from 0.10to 0.15% zirconium and from 0.5 to 0.9% hafnium, balance copper.

After the casting has been prepared according to the alloying procedureas described above, the material is amendable to extensive hot workingas by hot rolling, extruding or forging upon preheating the alloy toabout 980 C. in a charcoal bed. Heat treatment thereof is carried out bysolution annealing in a non-oxidizing atmosphere at a temperature offrom about 900 to 980 C. and preferably at about 950 to 965 C. for aperiod of from a few minutes to about an hour depending upon the size ofthe casting. The solution annealed and quenched alloy may then be agedsuitably at temperatures of from 300 to 600 C. and preferably between400 and 550 C. with or without cold working of the material between thesolution annealing and precipitation hardening or aging steps. Ingeneral, maximum proper ties are developed with an aging period of fromone to two hours with best results being obtained by aging at from 500to 55-0 C. when the material has not been cold worked and attemperatures of from 400 to 500 and preferably at about 450 C. when thealloy has been subjected to intermediate cold working.

Representative alloys of the present invention are listed in Table 1.The properties shown for the various alloys referred to therein weredetermined on unaged material after one inch diameter castings were hotrolled to 0.25 inch rods, said rods being solution annealed at 980 C.for one hour, quenched in water and then cold drawn to 0.081 inchdiameter wire with reduction.

TABLE 1 Room temperature properties of Cu-Zr-Hf alloys (before sComposition Elonga- Electrical Casting Tensile Yield tion perconduco.stren th strength cent (in ti ity Percent Percent (p.s.i.) (p.s.i.) 2inches) (percent Zr H1 I.A.O.S.

The same alloys upon being aged at 400 C. for one hour possessed theproperties shown in Table 2.

TABLE 2 Room temperature propertzes 0f Cu-Zr-Hf alloys (after aging)Composition Elonga- Electrical Casting Tensile Yield tion perconduc- No.strength strengti cent (in tivity Percent Percent (p.s.i.) (p.s.i.) 2inches) (percent The effect of varying the aging temperature on theproperties of two representative alloys is shown by the 3 data in Table3. The alloys having the composition 0.04% Zr, 0.66% Hf, balance Cu(Alloy A) and 0.11% Zr, 0.63% Hf, balance Cu (Alloy B) were processed bysolution annealing at 965 C. for one hour,

quenching, cold drawing to 0.081 inch diameter wire with 90% reductionafter which the material was aged as stated in Table 3.

TABLE 3 Efiect of temperature on cold worked Cu-Zr-Hf alloy wire TensileYield Elonga- Alloy Treatment Strength strength tion per- (p.s.i.)(p.s.i.) cent (in 2 inches) Cold worked condition 70,000 06,000 2. 4Heated at 300 0., 1 hour 71,000 65,000 8.0 Heated at 350 0., 1 hour"..-76, 500 68,000 11.0 Heated at 400 0., 1 hour 80,000 72,000 9.0 Heated at450 0., 1 hour 77,000 72,000 9. Heated at 500 71,000 04, 000 0. 0 Heatedat 550 1 62,000 55,000 0.0 Heated at 600 1 53,400 42,000 15.0 Heated at650 1 42,000 21,000 28. 0 Heated at 700 1 38,500 14,000 34.0 Cold worked00 151 71,000 63,000 4.0 Heated at 300 0 1 75, 300 69,200 9. 2 Heated at350 0 1 78, 800 72, 000 13. 0 Heated at 400 0., 1 30, 000 73, 000 12. 0Heated at 450 0., 1 79, 000 73, 000 8. 8 Heated at 500 0., 1 71,500 04,400 8. 8 Heated at 550 0., 1 63,500 54,800 11.0 Heated at 600 0., 1 ,50036,000 17. 6 Heated at 050 0., 1 hour-.. 40,500 18,000 33.0 Heated at700 0., 1 hour 39,500 17,000 26. 0

As will be noted from Table 1, the electrical conductivity of the alloycontaining 0.11% Zr, 0.63% Hf in the cold worked and unaged condition is41% I.A.C.S. After aging for 1 hour at temperatures of 450 and 500 C.,however, the electrical conductivity of the same alloy rose to values of80 and 84% I.A.C.S. respectively.

The efiect of aging at different temperatures after solution annealingthe alloy is seen from the data presented in Table 4. In these tests thealloys containing 0.04% Zr, 0.66% Hf, balance copper (Alloy A) and 0.11%Zr, 0.63% Hf, balance copper (Alloy B) were processed into 0.178 inchdiameter cold drawn wire, solution annealed at 965 C. for one hour,quenched and then heated for one hour at the specified temperatures.

TABLE 4 Properties of solution annealed and aged Cu-Zr-Hf alloysElong'a- Electrical Tensile Yield tion perconduc- Treatment strengthstrength cent (in tivity (p.s.i.) (p.s.i.) 2 inches) (percent ALLOY "A"S01. anneal 1 hr. at 965 C.

quench 34,000 5,600 40.0 41. 7 So]. anneal-age 1 hr. at 400 C. 35, 0007,000 40. 0 43.0 Sol. anneal-age 1 hr. at 450 0. 33,000 7,000 40.0 44. 0s01. anneal-age 1hr. at 500 0 33,000 8,000 43.0 43.0 Sol. anneal-age 1hr. at 550 (1 39,000 19,000 34. 0 83. 0 Sol.anneal-age1hr.at 600 0.35,000 15,000 35.0 82.0

ALLOY B Sol. anneal 1 hr. at 965 C.

quench 35,000 6,000 40.0 450 S01. anneal-age 1 hr. at 400 C. 35, 0008,000 30. 0 48. 0 S01. anneal-age 1 hr. at 450 0. 38,000 8,000 38.0 47.0 S01. anneal-age 1 hr. at 500 0. 34,000 11,000 38.0 47.0 Sol.anneal-age 1 hr. at 550 0. 41,000 20,000 40.0 86. 0 S01. anneal-age 1hr. at 600 C. 38,000 14,000 38. 0 85. 0

It will be noted from the above data that maximum precipitationhardening occurs at 550 C. This is about 50 C. higher than other copperbase alloys and indicates the superior high temperature properties ofthe present alloys. It will also be noted that the properties of thehigher zirconium content alloy are slightly superior to the alloycontaining 0.04% Zr.

The effect of variation in the extent of cold working TABLE 5 Propertiesof solution annealed, cold worked and aged Cu-Zr-Hf alloy Tensile YieldElong, Elec. Treatment strength strength (percent 00nd.

(p.s.i.) (p.s.i.) in 2 (percent,

inches) LA.C.S.)

Sol. anneal 1 hr. at 965 C 35, 000 6. 000 40. 0 45. 0 Sol. anneal-age 1hr. at 550 C. 41, 000 17,000 40.0 86. 0 S01. anneal cold work 25%.. 51,000 48, 000 5.0 45.0 Sol. anneal cold Work 55% 62,000 59,000 3.0 44.0Sol. anneal cold Work 67,000 63,000 3.0 44. 0 S01. anneal cold Work71,000 63,000 4.0 41.0 Sol. anneal-cold Work 25%- age 2 hrs. at 400 C65,000 55, 000 14.0 60. 0 S01. anneal-cold work 55%- age 2 hrs. at; 400C 72, 000 65, 000 10. 0 08.0 Sol. anneal-cold Work 75%- age 2 hrs. at400 C 76, 000 08, 000 12.0 68.0 Sol. anneal cold work 90%- age 2 hrs. at400 C 80,000 72,000 12.0 66.0

The alloy of maximum tensile strength of 80,000 p.s.i. with 12%elongation and 66% electrical conductivity is obtained upon cold drawingto a reduction of 90% prior to aging the cold worked material.

The superior high temperature properties of the alloys of the presentinvention are made readily apparent by comparison of the hightemperature tensile and elongation properties thereof with other copperbase alloys such as copper-zirconium and copper-chromium which materialsare generally recognized as possessing superior high temperature.tensile strength and ductility. The procedure used in making thecomparison consisted of first aging the cold worked 0.081 inch diameterwire specimens of each of the alloys specified in Table 6 and allowingthe specimens to cool to room temperature. The aged and cooled specimenswere then reheated to 400 (2., held at this temperature for one hour andtensile strength tests were run at a crosshead speed of 0.02 inch perminute. The results are summarized in Table 6.

It will be noted that both of the tested Cu-Zr-Hf alloys not onlypossess superior tensile strength and elongation properties at 400 C.compared with the designated Cu- Zr, Cu-Cr and Cu-Hf alloys but alsothat the significant improvement with respect to such high temperatureproperties is not obtainable with the use of either zirconium or hafniumas the sole alloying ingredient for copper.

It is apparent that many differing embodiments of this invention may bemade without departing from the spirit and scope thereof and it is notintended to be limited thereby except as indicated in the appendedclaims.

What is claimed is:

1. An age hardenable copper base alloy containing from 0.02 to about0.15% zirconium, from 0.1 to about 1.2% hafnium and the remainderoxygen-free copper.

2. An age hardenable copper base alloy containing from 0.04 to about0.15 zirconium, 0.5 to about 1% hafnium, balance oxygen-free copper,said alloy being 5 6 characterized by superior high temperature tensilestrength from 0.02 to about 0.15% zirconium, 0.1 to about 1.2% andductility in the age hardened condition. hafnium and the remainderchemically deoxidized copper 3. An homogeneous copper alloy consistingof from with incidental impurities normally associated therewith.

0.1 to 0.15% zirconium, 0.5 to 0.9% hafnium, balance References Cfied inthe file of this patent copper with incidental impurities normallyassociated 5 therewith, said copper being oxygen-free prior to its beingUNITED STATES PATENTS alloyed with said zirconium and hafnium. 2,086,329Hensel et a1. July 6, 1937 4. An age hardenable copper-base alloycontaining 2,097,816 Hensel et a1. Nov. 2, 1937

1. AN AGE HARDENABLE COPPER BASE ALLOY CONTAINING FROM 0.02 TO ABOUT0.15% ZIRCONIUM, FROM 0.1 TO ABOUT 1.2% HAFNIUM AND THE REMAINDEROXYGEN-FREE COPPER